We attempt to make three composite Science and Technology (S&T) indices for overall understanding of national S&T by aggregation of various S&T indicators using fuzzy set theory and then use these Indices to compare the S&T activities of Korea with those of five developed countries (France, Germany, Japan, the U.K., the U.S.). The overall results suggest that although the S&T indices of Korea still lag behind those of developed countries, they have grown rapidly and continuously and, as a result, the S&T gaps between Korea and developed countries have narrowed. However, the capability of Korea to transform its R&D input into final economic output has not yet matched that of developed countries.